Lake Hancza

Hancza reaches 108.5 metres, which makes it the deepest lake in Poland and the deepest anywhere on the North European Plain - a subglacial trench melted under the ice and left as a narrow ribbon of water less than a kilometre wide with steep sides going straight down. The depth and the cold keep it exceptionally clear, and it is the best-known freshwater dive site in the country, with visibility that is good by Polish standards and a bottom of boulders and drop-offs; several dive operators work out of the villages on the shore. There is a relict fauna in it left over from colder conditions after the ice, including species otherwise found much further north. It sits inside the Suwalki Landscape Park, in a landscape of moraine hills that is one of the most sculpted in Poland, and the walk along the shore gives the shape of the trench better than a boat does.

What you actually see

• 108.5 metres deep - the deepest lake in Poland and on the North European Plain.
• A subglacial trench - under a kilometre wide with sides going straight down.
• A dive site - cold, clear water with boulder drop-offs and local operators.
• Moraine hills around it - inside the Suwalki Landscape Park.

When to go

June to September. Half a day, longer to dive.

Honest expectations

The water is very cold at depth all year and diving needs proper kit and a local operator. The shore is steep in places. Facilities are minimal. Winters here are the coldest in Poland.

Nearby

Suwalki Landscape Park surrounds it; Wigry is south-west.